Macro assertables::assume_fn_eq

macro_rules! assume_fn_eq {
    ($function:path, $left:expr, $right:expr $(,)?) => { ... };
    ($function:path, $left:expr, $right:expr, $($arg:tt)+) => { ... };
}

Assume one function output is equal to another function output.

• When true, return Ok(true).

• Otherwise, return Err with a message and the values of the expressions with their debug representations.

Example

assume_fn_eq!(i32::abs, 1 as i32, -1 as i32);
//-> Ok(true)

assume_fn_eq!(i32::abs, 1 as i32, -2 as i32);
//-> Err("assumption failed: `assume_fn_eq(left, right)`\n  left input: `1`\n right input: `2`\n  left output: `1`\n right output: `2`")

This macro has a second form where a custom message can be provided.